In the design and development of computer system networks, there are many considerations and trade-offs which must be balanced in order to provide an optimum system and to decide what limits must be drawn in terms of economic factors, size and space factors and versatility of control of the system.
The presently described computer network system is designed not only to be used with a variety of peripheral type devices but also with data comm and telephone lines to remote terminals to provide rapid transference of data between the units and rapid data processing by a central processing unit in a fashion whereby reliability is maintained to a very high degree.
The system is organized so that each of the various elements and units will, when initiated, provide its own self-test routines and report the results and information to a maintenance processor called the User Interface Processor 100. This processor works in conjunction with the various remote terminals, and the various types of peripheral devices through an I/O subsystem which is uniquely designed to handle units called "data link processors". These types of data link processing units were described in their earlier versions in U.S. Pat. Nos. 4,415,986; 4,392,207; 4,313,162; 4,390,964 and 4,386,415.
The maintenance subsystem involved herein is so interconnected to the various elements of the system that self-test data may be collected and transported to a remote diagnostic unit which may be a central diagnostic unit for many, many computer networks in many different locations. The remote terminal will perform the basic diagnostic routines to any of the computer networks which have problems and will send messages which pinpoint the specific cause or location of the trouble so that a local operator may correct the fault by changing a card, replacing a module or fixing any other designated fault or outness.